OP0151 MIRNAS CONTRIBUTE TO DYSREGULATED ROS METABOLISM OF IMMUNE CELLS IN THE INFLAMED JOINT
Authors: Kim Ohl, Patricia Klemm, Tobias Schwarz, Federica Raggi, Alessandro Consolaro, Joachim Peitz, Gerd Horneff, Klaus Tenbrock
Journal: Annals of the Rheumatic Diseases (2019)

<h3>Background</h3> In the last years miRNAs have emerged as critical regulators of innate and adaptive immune responses and an altered expression or function is associated with several inflammatory and autoimmune diseases. Therefore miRNAs are also believed to promote inflammatory processes within the inflamed joint of juvenile idiopathic arthritis (JIA) patients. It is furthermore known that oxidative stress is associated with JIA. Free radicals are implicated in joint damage and play an important role as secondary messengers in immunological responses. How and if miRNAs contribute to dysregulated reactive oxygen species (ROS) metabolism in JIA remains to be elucidated. <h3>Objectives</h3> We aimed to identify miRNAs and miRNA regulated pathways, which contribute to dysregulated immune cell responses within the inflamed joint. Methods: miRNA profiling was performed on peripheral blood mononuclear cells (PBMCs) from healthy children, PBMCS from 9 JIA patients and synovial fluid mononuclear cells (SFMCs) from the same JIA patients. Subsequently, GO and pathway enrichment analyses were performed on predicted target genes. Upregulation of miRNAs was confirmed <i>in vitro</i> after incubation with synovial fluid by qRT-PCR. Mitochondrial integrity, cellular ROS and Nrf2 protein expression were measured by flow cytometry. <h3>Results</h3> Transcriptome analysis of JIA SFMCs compared to HC PBMCs revealed strongly enhanced expression of <i>miR23a</i> and <i>miR23a</i>, <i>miR27a</i>, <i>miR146a</i>, and <i>miR155</i>, which are involved in oxidative stress responses. In addition, expression of those could be induced in healthy control PBMCs by synovial fluid <i>ex vivo</i>. ROS level in synovial fluid T cells were enhanced, while expression of Nrf2, the main regulator of anti-oxidative responses and a target of <i>miR27a</i>, remained low. Furthermore mitochondrial cyclophilin, which regulates ROS escape from mitochondria and is suppressed by <i>miR23a</i>, was downregulated in SFMCs as well. <h3>Conclusion</h3> SFMCs within the inflamed joint reveal a distinct miRNA expression profile. Especially miRNAs that are involved in regulation of ROS metabolism are upregulated. In line with this, expression of Nrf2 and mitochondrial cyclophilin which are important regulators of cellular ROS metabolism are reduced while production of ROS is enhanced. We suggest that higher abundance of miRNAs, that are involved in oxidative stress pathways, contribute to redox dysregulations within the inflamed joint and thereby contribute to inflammatory processes. <h3> Disclosure of Interests:&nbsp;</h3> Kim Ohl: None declared, Patricia Klemm: None declared, Tobias Schwarz: None declared, federica Raggi: None declared, Alessandro Consolaro Grant/research support from: AbbVie, Pfizer, Joachim Peitz: None declared, Gerd Horneff: None declared, Klaus Tenbrock Grant/research support from: Pfizer, BMS, Novartis, Speakers bureau: Pfizer, Novartis